This rest of the Very English Mystery series was fantastic, but this just wasn't. Has no plot, no real conflict, no real mystery, no climax, and an utterly predictable conclusion. If you're reading the Very English Mystery series, which I highly recommend, you should read #1, then #2, and skip #1.5 (this book). You won't miss anything.
If you (like me) like the characters in the Very English Mystery series, then maybe you want to read this book, just to visit them again. But honestly, they don't do much very interesting here, and it feels contrived (more contrived than the full-length novels).